High density timing based servo format

ABSTRACT

A product according to one embodiment includes a magnetic recording tape having opposite ends and at least one servo track, a longitudinal axis of the magnetic recording tape being defined between the ends. The at least one servo track has a plurality of straight first magnetic bars, and a plurality of straight second magnetic bars spaced from the first magnetic bars. A width of each of the at least one servo track is defined in a direction perpendicular to the longitudinal axis of the magnetic recording tape between sides of the servo track, the sides of each servo track extending along opposite ends of the each of the first magnetic bars. Lengths of the second magnetic bars between outermost ends thereof are less than the width of the associated servo track.

BACKGROUND

The present invention relates to data storage systems, and moreparticularly, this invention relates to a high density timing basedservo format, a tape having said servo format, and related apparatusescompatible therewith.

In magnetic storage systems, data is read from and written onto magneticrecording media utilizing magnetic transducers. Data is written on themagnetic recording media by moving a magnetic recording transducer to aposition over the media where the data is to be stored. The magneticrecording transducer then generates a magnetic field, which encodes thedata into the magnetic media. Data is read from the media by similarlypositioning the magnetic read transducer and then sensing the magneticfield of the magnetic media. Read and write operations may beindependently synchronized with the movement of the media to ensure thatthe data can be read from and written to the desired location on themedia.

An important and continuing goal in the data storage industry is that ofincreasing the density of data stored on a medium. For tape storagesystems, that goal has led to increasing the track and linear bitdensity on recording tape, and decreasing the thickness of the magnetictape medium. However, the development of small footprint, higherperformance tape drive systems has created various problems in thedesign of a tape head assembly for use in such systems.

In a tape drive system, magnetic tape is moved over the surface of thetape head at high speed. Usually the tape head is designed to minimizethe spacing between the head and the tape. The spacing between themagnetic head and the magnetic tape is crucial and so goals in thesesystems are to have the recording gaps of the transducers, which are thesource of the magnetic recording flux in near contact with the tape toeffect writing sharp transitions, and to have the read elements in nearcontact with the tape to provide effective coupling of the magneticfield from the tape to the read elements.

BRIEF SUMMARY

A product according to one embodiment includes a magnetic recording tapehaving opposite ends and at least one servo track, a longitudinal axisof the magnetic recording tape being defined between the ends. The atleast one servo track has a plurality of straight first magnetic bars,and a plurality of straight second magnetic bars spaced from the firstmagnetic bars. A width of each of the at least one servo track isdefined in a direction perpendicular to the longitudinal axis of themagnetic recording tape between sides of the servo track, the sides ofeach servo track extending along opposite ends of the each of the firstmagnetic bars. Lengths of the second magnetic bars between outermostends thereof are less than the width of the associated servo track.

An apparatus according to one embodiment includes a magnetic head; adrive mechanism for passing such a magnetic recording tape over themagnetic head; and a controller electrically coupled to the magnetichead, the controller being configured to decode the servo track(s) ofthe magnetic recording tape.

An apparatus according to another embodiment includes a magnetic headhaving at least one servo writer for writing the magnetic bars to amagnetic recording tape; a drive mechanism for passing the magneticrecording tape over the magnetic head; and a controller electricallycoupled to the magnetic head.

A computer program product for writing servo tracks on a magneticrecording tape according to one embodiment includes a computer readablestorage medium having program instructions embodied therewith. Thecomputer readable storage medium is not a transitory signal per se. Theprogram instructions are executable by a controller to cause thecontroller to perform a method including writing at least one servotrack on a magnetic recording tape. The at least one servo track has aplurality of first magnetic bars and a plurality of second magneticbars. A width of each of the at least one servo track is defined betweensides of the servo track in a direction perpendicular to thelongitudinal axis of the magnetic recording tape, where the sides ofeach servo track extending along ends of the first magnetic bars.Lengths of the second magnetic bars along the longitudinal axes thereofare less than the width of the associated servo track. The secondmagnetic bars each have a longitudinal axis oriented substantially 90degrees from the longitudinal axis of the magnetic recording tape.

A controller-implemented method according to one embodiment includescausing, by the controller, reading of at least one servo track of amagnetic recording tape, the at least one servo track having a pluralityof straight first magnetic bars and a plurality of straight secondmagnetic bars spaced from the first magnetic bars. A width of each ofthe at least one servo track is defined in a direction perpendicular toa longitudinal axis of the magnetic recording tape between sides of theservo track, the sides of each servo track extending along opposing endsof each of the first magnetic bars. Lengths of the second magnetic barsbetween outermost ends thereof are less than the width of the associatedservo track. The method further includes deriving, by the controller, atleast one of velocity and skew information from reading the at least oneservo track.

A product according to yet another embodiment includes a magneticrecording tape having opposite ends and at least one servo track, alongitudinal axis of the magnetic recording tape being defined betweenthe ends. The at least one servo track has a plurality of first magneticbars and a plurality of second magnetic bars. A width of each of the atleast one servo track is defined in a direction perpendicular to thelongitudinal axis of the magnetic recording tape between sides of theservo track, the sides of each servo track extending along ends of thefirst magnetic bars. Lengths of at least some the second magnetic barsbetween outer ends thereof are greater than one half the width of theassociated servo track and less than the width of the associated servotrack.

Other aspects and embodiments of the present invention will becomeapparent from the following detailed description, which, when taken inconjunction with the drawings, illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a schematic diagram of a simplified tape drive systemaccording to one embodiment.

FIG. 1B is a schematic diagram of a tape cartridge according to oneembodiment.

FIG. 2 illustrates a side view of a flat-lapped, bi-directional,two-module magnetic tape head according to one embodiment.

FIG. 2A is a tape bearing surface view taken from Line 2A of FIG. 2.

FIG. 2B is a detailed view taken from Circle 2B of FIG. 2A.

FIG. 2C is a detailed view of a partial tape bearing surface of a pairof modules.

FIG. 3 is a partial tape bearing surface view of a magnetic head havinga write-read-write configuration.

FIG. 4 is a partial tape bearing surface view of a magnetic head havinga read-write-read configuration.

FIG. 5 is a side view of a magnetic tape head with three modulesaccording to one embodiment where the modules all generally lie alongabout parallel planes.

FIG. 6 is a side view of a magnetic tape head with three modules in atangent (angled) configuration.

FIG. 7 is a side view of a magnetic tape head with three modules in anoverwrap configuration.

FIG. 8A is a partial side representational view of a magnetic recordingtape according to one embodiment.

FIG. 8B is a detail representational view of the magnetic recording tapetaken from box AA of FIG. 8A, according to one embodiment.

FIG. 8C is a detail representational view of an alternate embodiment ofthe magnetic recording tape of FIG. 8B.

FIG. 8D is a detail representational view of an alternate embodiment ofthe magnetic recording tape of FIG. 8B.

FIG. 9 is a side view of an apparatus for writing a servo pattern on amagnetic recording tape, according to one embodiment.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating thegeneral principles of the present invention and is not meant to limitthe inventive concepts claimed herein. Further, particular featuresdescribed herein can be used in combination with other describedfeatures in each of the various possible combinations and permutations.

Unless otherwise specifically defined herein, all terms are to be giventheir broadest possible interpretation including meanings implied fromthe specification as well as meanings understood by those skilled in theart and/or as defined in dictionaries, treatises, etc.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an” and “the” include pluralreferents unless otherwise specified.

The following description discloses several preferred embodiments ofmagnetic storage systems, as well as operation and/or component partsthereof.

In one general embodiment, a product includes a magnetic recording tapehaving opposite ends, a longitudinal axis of the magnetic recording tapebeing defined between the ends. The magnetic recording tape has at leastone servo track, the at least one servo track having a plurality offirst magnetic bars and a plurality of second magnetic bars. The firstmagnetic bars each have a longitudinal axis oriented between 2 and 88degrees from the longitudinal axis of the magnetic recording tape. Awidth of each of the at least one servo track is defined in a directionperpendicular to the longitudinal axis of the magnetic recording tapebetween sides of the servo track, the sides of each servo trackextending along ends of the first magnetic bars. Lengths of the secondmagnetic bars along the longitudinal axes thereof are less than thewidth of the associated servo track.

An apparatus according to one embodiment includes a magnetic head; adrive mechanism for passing such a magnetic recording tape over themagnetic head; and a controller electrically coupled to the magnetichead.

An apparatus according to another embodiment includes a magnetic headhaving at least one servo writer for writing the magnetic bars to amagnetic recording tape; a drive mechanism for passing the magneticrecording tape over the magnetic head; and a controller electricallycoupled to the magnetic head.

In another general embodiment, a method includes writing at least oneservo track on a magnetic recording tape. The at least one servo trackhas a plurality of first magnetic bars and a plurality of secondmagnetic bars. The first magnetic bars each having a longitudinal axisoriented between 2 and 88 degrees from the longitudinal axis of themagnetic recording tape. A width of each of the at least one servo trackis defined between sides of the servo track in a direction perpendicularto the longitudinal axis of the magnetic recording tape, where the sidesof each servo track extending along ends of the first magnetic bars.Lengths of the second magnetic bars along the longitudinal axes thereofare less than the width of the associated servo track.

An apparatus according to one embodiment includes a magnetic head havingat least one servo writer to perform the foregoing method; a drivemechanism for passing the magnetic recording tape over the magnetichead; and a controller electrically coupled to the magnetic head.

An apparatus according to another embodiment includes a magnetic head; adrive mechanism for passing a magnetic recording tape over the magnetichead; and a controller electrically coupled to the magnetic head, thecontroller being configured to perform the foregoing method.

FIG. 1A illustrates a simplified tape drive 100 of a tape-based datastorage system, which may be employed in the context of the presentinvention. While one specific implementation of a tape drive is shown inFIG. 1A, it should be noted that the embodiments described herein may beimplemented in the context of any type of tape drive system.

As shown, a tape supply cartridge 120 and a take-up reel 121 areprovided to support a tape 122. One or more of the reels may form partof a removable cartridge and are not necessarily part of the system 100.The tape drive, such as that illustrated in FIG. 1A, may further includedrive motor(s) to drive the tape supply cartridge 120 and the take-upreel 121 to move the tape 122 over a tape head 126 of any type. Suchhead may include an array of readers, writers, or both.

Guides 125 guide the tape 122 across the tape head 126. Such tape head126 is in turn coupled to a controller 128 via a cable 130. Thecontroller 128, may be or include a processor and/or any logic forcontrolling any subsystem of the drive 100. For example, the controller128 typically controls head functions such as servo following, datawriting, data reading, etc. The controller 128 may operate under logicknown in the art, as well as any logic disclosed herein. The controller128 may be coupled to a memory 136 of any known type, which may storeinstructions executable by the controller 128. Moreover, the controller128 may be configured and/or programmable to perform or control some orall of the methodology presented herein. Thus, the controller may beconsidered configured to perform various operations by way of logicprogrammed into a chip; software, firmware, or other instructions beingavailable to a processor; etc. and combinations thereof.

The cable 130 may include read/write circuits to transmit data to thehead 126 to be recorded on the tape 122 and to receive data read by thehead 126 from the tape 122. An actuator 132 controls position of thehead 126 relative to the tape 122.

An interface 134 may also be provided for communication between the tapedrive 100 and a host (integral or external) to send and receive the dataand for controlling the operation of the tape drive 100 andcommunicating the status of the tape drive 100 to the host, all as willbe understood by those of skill in the art.

FIG. 1B illustrates an exemplary tape cartridge 150 according to oneembodiment. Such tape cartridge 150 may be used with a system such asthat shown in FIG. 1A. As shown, the tape cartridge 150 includes ahousing 152, a tape 122 in the housing 152, and a nonvolatile memory 156coupled to the housing 152. In some approaches, the nonvolatile memory156 may be embedded inside the housing 152, as shown in FIG. 1B. In moreapproaches, the nonvolatile memory 156 may be attached to the inside oroutside of the housing 152 without modification of the housing 152. Forexample, the nonvolatile memory may be embedded in a self-adhesive label154. In one preferred embodiment, the nonvolatile memory 156 may be aFlash memory device, ROM device, etc., embedded into or coupled to theinside or outside of the tape cartridge 150. The nonvolatile memory isaccessible by the tape drive and the tape operating software (the driversoftware), and/or other device.

By way of example, FIG. 2 illustrates a side view of a flat-lapped,bi-directional, two-module magnetic tape head 200 which may beimplemented in the context of the present invention. As shown, the headincludes a pair of bases 202, each equipped with a module 204, and fixedat a small angle α with respect to each other. The bases may be“U-beams” that are adhesively coupled together. Each module 204 includesa substrate 204A and a closure 204B with a thin film portion, commonlyreferred to as a “gap” in which the readers and/or writers 206 areformed. In use, a tape 208 is moved over the modules 204 along a media(tape) bearing surface 209 in the manner shown for reading and writingdata on the tape 208 using the readers and writers. The wrap angle θ ofthe tape 208 at edges going onto and exiting the flat media supportsurfaces 209 are usually between about 0.1 degree and about 5 degrees.

The substrates 204A are typically constructed of a wear resistantmaterial, such as a ceramic. The closures 204B made of the same orsimilar ceramic as the substrates 204A.

The readers and writers may be arranged in a piggyback or mergedconfiguration. An illustrative piggybacked configuration comprises a(magnetically inductive) writer transducer on top of (or below) a(magnetically shielded) reader transducer (e.g., a magnetoresistivereader, etc.), wherein the poles of the writer and the shields of thereader are generally separated. An illustrative merged configurationcomprises one reader shield in the same physical layer as one writerpole (hence, “merged”). The readers and writers may also be arranged inan interleaved configuration. Alternatively, each array of channels maybe readers or writers only. Any of these arrays may contain one or moreservo track readers for reading servo data on the medium.

FIG. 2A illustrates the tape bearing surface 209 of one of the modules204 taken from Line 2A of FIG. 2. A representative tape 208 is shown indashed lines. The module 204 is preferably long enough to be able tosupport the tape as the head steps between data bands.

In this example, the tape 208 includes 4 to 22 data bands, e.g., with 16data bands and 17 servo tracks 210, as shown in FIG. 2A on a one-halfinch wide tape 208. The data bands are defined between servo tracks 210.Each data band may include a number of data tracks, for example 1024data tracks (not shown). During read/write operations, the readersand/or writers 206 are positioned to specific track positions within oneof the data bands. Outer readers, sometimes called servo readers, readthe servo tracks 210. The servo signals are in turn used to keep thereaders and/or writers 206 aligned with a particular set of tracksduring the read/write operations.

The servo tracks 210 also preferably include magnetic bars, e.g., seeFIG. 8. As an option, the magnetic bars may provide a magnetic head withrun-time information, which may include, but is not limited to speed ofthe tape, longitudinal and/or cross track positioning along the tape,etc. as will be discussed in further detail below.

Referring now to FIG. 2B, the detailed view depicts a plurality ofreaders and/or writers 206 formed in a gap 218 on the module 204 inCircle 2B of FIG. 2A. As shown, the array of readers and writers 206includes, for example, 16 writers 214, 16 readers 216 and two servoreaders 212, though the number of elements may vary. Illustrativeembodiments include 8, 16, 32, 40, and 64 active readers and/or writers206 per array, and alternatively interleaved designs having odd numbersof reader or writers such as 17, 25, 33, etc. An illustrative embodimentincludes 32 readers per array and/or 32 writers per array, where theactual number of transducer elements could be greater, e.g., 33, 34,etc. This allows the tape to travel more slowly, thereby reducingspeed-induced tracking and mechanical difficulties and/or execute fewer“wraps” to fill or read the tape. While the readers and writers may bearranged in a piggyback configuration as shown in FIG. 2B, the readers216 and writers 214 may also be arranged in an interleavedconfiguration. Alternatively, each array of readers and/or writers 206may be readers or writers only, and the arrays may contain one or moreservo readers 212. As noted by considering FIGS. 2 and 2A-B together,each module 204 may include a complementary set of readers and/orwriters 206 for such things as bi-directional reading and writing,read-while-write capability, backward compatibility, etc.

FIG. 2C shows a partial tape bearing surface view of complimentarymodules of a magnetic tape head 200 according to one embodiment. In thisembodiment, each module has a plurality of read/write (R/W) pairs in apiggyback configuration formed on a common substrate 204A and anoptional electrically insulative layer 236. The writers, exemplified bythe write head 214 and the readers, exemplified by the read head 216,are aligned parallel to an intended direction of travel of a tape mediumthereacross to form an R/W pair, exemplified by the R/W pair 222. Notethat the intended direction of tape travel is sometimes referred toherein as the direction of tape travel, and such terms may be usedinterchangeable. Such direction of tape travel may be inferred from thedesign of the system, e.g., by examining the guides; observing theactual direction of tape travel relative to the reference point; etc.Moreover, in a system operable for bi-direction reading and/or writing,the direction of tape travel in both directions is typically paralleland thus both directions may be considered equivalent to each other.

Several R/W pairs 222 may be present, such as 8, 16, 32 pairs, etc. TheR/W pairs 222 as shown are linearly aligned in a direction generallyperpendicular to a direction of tape travel thereacross. However, thepairs may also be aligned diagonally, etc. Servo readers 212 arepositioned on the outside of the array of R/W pairs, the function ofwhich is well known.

Generally, the magnetic tape medium moves in either a forward or reversedirection as indicated by arrow 220. The magnetic tape medium and headassembly 200 operate in a transducing relationship in the mannerwell-known in the art. The piggybacked MR head assembly 200 includes twothin-film modules 224 and 226 of generally identical construction.

Modules 224 and 226 are joined together with a space present betweenclosures 204B thereof (partially shown) to form a single physical unitto provide read-while-write capability by activating the writer of theleading module and reader of the trailing module aligned with the writerof the leading module parallel to the direction of tape travel relativethereto. When a module 224, 226 of a piggyback head 200 is constructed,layers are formed in the gap 218 created above an electricallyconductive substrate 204A (partially shown), e.g., of AlTiC, ingenerally the following order for the R/W pairs 222: an insulating layer236, a first shield 232 typically of an iron alloy such as NiFe (—), CZTor Al—Fe—Si (Sendust), a sensor 234 for sensing a data track on amagnetic medium, a second shield 238 typically of a nickel-iron alloy(e.g., ˜80/20 at % NiFe, also known as permalloy), first and secondwriter pole tips 228, 230, and a coil (not shown). The sensor may be ofany known type, including those based on MR, GMR, AMR, tunnelingmagnetoresistance (TMR), etc.

The first and second writer poles 228, 230 may be fabricated from highmagnetic moment materials such as ˜45/55 NiFe. Note that these materialsare provided by way of example only, and other materials may be used.Additional layers such as insulation between the shields and/or poletips and an insulation layer surrounding the sensor may be present.Illustrative materials for the insulation include alumina and otheroxides, insulative polymers, etc.

The configuration of the tape head 126 according to one embodimentincludes multiple modules, preferably three or more. In awrite-read-write (W-R-W) head, outer modules for writing flank one ormore inner modules for reading. Referring to FIG. 3, depicting a W-R-Wconfiguration, the outer modules 252, 256 each include one or morearrays of writers 260. The inner module 254 of FIG. 3 includes one ormore arrays of readers 258 in a similar configuration. Variations of amulti-module head include a R-W-R head (FIG. 4), a R-R-W head, a W-W-Rhead, etc. In yet other variations, one or more of the modules may haveread/write pairs of transducers. Moreover, more than three modules maybe present. In further approaches, two outer modules may flank two ormore inner modules, e.g., in a W-R-R-W, a R-W-W-R arrangement, etc. Forsimplicity, a W-R-W head is used primarily herein to exemplifyembodiments of the present invention. One skilled in the art apprisedwith the teachings herein will appreciate how permutations of thepresent invention would apply to configurations other than a W-R-Wconfiguration.

FIG. 5 illustrates a magnetic head 126 according to one embodiment ofthe present invention that includes first, second and third modules 302,304, 306 each having a tape bearing surface 308, 310, 312 respectively,which may be flat, contoured, etc. Note that while the term “tapebearing surface” appears to imply that the surface facing the tape 315is in physical contact with the tape bearing surface, this is notnecessarily the case. Rather, only a portion of the tape may be incontact with the tape bearing surface, constantly or intermittently,with other portions of the tape riding (or “flying”) above the tapebearing surface on a layer of air, sometimes referred to as an “airbearing”. The first module 302 will be referred to as the “leading”module as it is the first module encountered by the tape in a threemodule design for tape moving in the indicated direction. The thirdmodule 306 will be referred to as the “trailing” module. The trailingmodule follows the middle module and is the last module seen by the tapein a three module design. The leading and trailing modules 302, 306 arereferred to collectively as outer modules. Also note that the outermodules 302, 306 will alternate as leading modules, depending on thedirection of travel of the tape 315.

In one embodiment, the tape bearing surfaces 308, 310, 312 of the first,second and third modules 302, 304, 306 lie on about parallel planes(which is meant to include parallel and nearly parallel planes, e.g.,between parallel and tangential as in FIG. 6), and the tape bearingsurface 310 of the second module 304 is above the tape bearing surfaces308, 312 of the first and third modules 302, 306. As described below,this has the effect of creating the desired wrap angle α₂ of the taperelative to the tape bearing surface 310 of the second module 304.

Where the tape bearing surfaces 308, 310, 312 lie along parallel ornearly parallel yet offset planes, intuitively, the tape should peel offof the tape bearing surface 308 of the leading module 302. However, thevacuum created by the skiving edge 318 of the leading module 302 hasbeen found by experimentation to be sufficient to keep the tape adheredto the tape bearing surface 308 of the leading module 302. The trailingedge 320 of the leading module 302 (the end from which the tape leavesthe leading module 302) is the approximate reference point which definesthe wrap angle α₂ over the tape bearing surface 310 of the second module304. The tape stays in close proximity to the tape bearing surface untilclose to the trailing edge 320 of the leading module 302. Accordingly,read and/or write elements 322 may be located near the trailing edges ofthe outer modules 302, 306. These embodiments are particularly adaptedfor write-read-write applications.

A benefit of this and other embodiments described herein is that,because the outer modules 302, 306 are fixed at a determined offset fromthe second module 304, the inner wrap angle α₂ is fixed when the modules302, 304, 306 are coupled together or are otherwise fixed into a head.The inner wrap angle α₂ is approximately tan⁻¹(δ/W) where δ is theheight difference between the planes of the tape bearing surfaces 308,310 and W is the width between the opposing ends of the tape bearingsurfaces 308, 310. An illustrative inner wrap angle α₂ is in a range ofabout 0.5° to about 1.1°, though can be any angle required by thedesign.

Beneficially, the inner wrap angle α₂ on the side of the module 304receiving the tape (leading edge) will be larger than the inner wrapangle α₃ on the trailing edge, as the tape 315 rides above the trailingmodule 306. This difference is generally beneficial as a smaller α₃tends to oppose what has heretofore been a steeper exiting effectivewrap angle.

Note that the tape bearing surfaces 308, 312 of the outer modules 302,306 are positioned to achieve a negative wrap angle at the trailing edge320 of the leading module 302. This is generally beneficial in helpingto reduce friction due to contact with the trailing edge 320, providedthat proper consideration is given to the location of the crowbar regionthat forms in the tape where it peels off the head. This negative wrapangle also reduces flutter and scrubbing damage to the elements on theleading module 302. Further, at the trailing module 306, the tape 315flies over the tape bearing surface 312 so there is virtually no wear onthe elements when tape is moving in this direction. Particularly, thetape 315 entrains air and so will not significantly ride on the tapebearing surface 312 of the third module 306 (some contact may occur).This is permissible, because the leading module 302 is writing while thetrailing module 306 is idle.

Writing and reading functions are performed by different modules at anygiven time. In one embodiment, the second module 304 includes aplurality of data and optional servo readers 331 and no writers. Thefirst and third modules 302, 306 include a plurality of writers 322 andno data readers, with the exception that the outer modules 302, 306 mayinclude optional servo readers. The servo readers may be used toposition the head during reading and/or writing operations. The servoreader(s) on each module are typically located towards the end of thearray of readers or writers.

By having only readers or side by side writers and servo readers in thegap between the substrate and closure, the gap length can besubstantially reduced. Typical heads have piggybacked readers andwriters, where the writer is formed above each reader. A typical gap is25-35 microns. However, irregularities on the tape may tend to droopinto the gap and create gap erosion. Thus, the smaller the gap is thebetter. The smaller gap enabled herein exhibits fewer wear relatedproblems.

In some embodiments, the second module 304 has a closure, while thefirst and third modules 302, 306 do not have a closure. Where there isno closure, preferably a hard coating is added to the module. Onepreferred coating is diamond-like carbon (DLC).

In the embodiment shown in FIG. 5, the first, second, and third modules302, 304, 306 each have a closure 332, 334, 336, which extends the tapebearing surface of the associated module, thereby effectivelypositioning the read/write elements away from the edge of the tapebearing surface. The closure 332 on the second module 304 can be aceramic closure of a type typically found on tape heads. The closures334, 336 of the first and third modules 302, 306, however, may beshorter than the closure 332 of the second module 304 as measuredparallel to a direction of tape travel over the respective module. Thisenables positioning the modules closer together. One way to produceshorter closures 334, 336 is to lap the standard ceramic closures of thesecond module 304 an additional amount. Another way is to plate ordeposit thin film closures above the elements during thin filmprocessing. For example, a thin film closure of a hard material such asSendust or nickel-iron alloy (e.g., 45/55) can be formed on the module.

With reduced-thickness ceramic or thin film closures 334, 336 or noclosures on the outer modules 302, 306, the write-to-read gap spacingcan be reduced to less than about 1 mm, e.g., about 0.75 mm, or 50% lessthan standard LTO tape head spacing. The open space between the modules302, 304, 306 can still be set to approximately 0.5 to 0.6 mm, which insome embodiments is ideal for stabilizing tape motion over the secondmodule 304.

Depending on tape tension and stiffness, it may be desirable to anglethe tape bearing surfaces of the outer modules relative to the tapebearing surface of the second module. FIG. 6 illustrates an embodimentwhere the modules 302, 304, 306 are in a tangent or nearly tangent(angled) configuration. Particularly, the tape bearing surfaces of theouter modules 302, 306 are about parallel to the tape at the desiredwrap angle α₂ of the second module 304. In other words, the planes ofthe tape bearing surfaces 308, 312 of the outer modules 302, 306 areoriented at about the desired wrap angle α₂ of the tape 315 relative tothe second module 304. The tape will also pop off of the trailing module306 in this embodiment, thereby reducing wear on the elements in thetrailing module 306. These embodiments are particularly useful forwrite-read-write applications. Additional aspects of these embodimentsare similar to those given above.

Typically, the tape wrap angles may be set about midway between theembodiments shown in FIGS. 5 and 6.

FIG. 7 illustrates an embodiment where the modules 302, 304, 306 are inan overwrap configuration. Particularly, the tape bearing surfaces 308,312 of the outer modules 302, 306 are angled slightly more than the tape315 when set at the desired wrap angle α₂ relative to the second module304. In this embodiment, the tape does not pop off of the trailingmodule, allowing it to be used for writing or reading. Accordingly, theleading and middle modules can both perform reading and/or writingfunctions while the trailing module can read any just-written data.Thus, these embodiments are preferred for write-read-write,read-write-read, and write-write-read applications. In the latterembodiments, closures should be wider than the tape canopies forensuring read capability. The wider closures may require a widergap-to-gap separation. Therefore a preferred embodiment has awrite-read-write configuration, which may use shortened closures thatthus allow closer gap-to-gap separation.

Additional aspects of the embodiments shown in FIGS. 6 and 7 are similarto those given above.

A 32 channel version of a multi-module head 126 may use cables 350having leads on the same or smaller pitch as current 16 channelpiggyback LTO modules, or alternatively the connections on the modulemay be organ-keyboarded for a 50% reduction in cable span. Over-under,writing pair unshielded cables may be used for the writers, which mayhave integrated servo readers.

The outer wrap angles α₁ may be set in the drive, such as by guides ofany type known in the art, such as adjustable rollers, slides, etc. Forexample, rollers having an offset axis may be used to set the wrapangles. The offset axis creates an orbital arc of rotation, allowingprecise alignment of the wrap angle α₁.

To assemble any of the embodiments described above, conventional u-beamassembly can be used. Accordingly, the mass of the resultant head may bemaintained or even reduced relative to heads of previous generations. Inother approaches, the modules may be constructed as a unitary body.Those skilled in the art, armed with the present teachings, willappreciate that other known methods of manufacturing such heads may beadapted for use in constructing such heads.

As alluded to above, timing based servo tracks preferably provideinformation about tapes during reading and/or writing operations. Suchservo tracks may provide information to the drive regarding the crosstrack (lateral) position of the head relative to a data band flanked bythe servo tracks. In various approaches, the servo tracks may includeadditional information, such as information that allows the drive todetermine the speed of the tape, longitudinal positioning along thetape, etc.

Various embodiments described herein provide timing based servo trackswhich increase, and in some approaches about double, the amount of servoinformation in the same physical space on a given tape, relative toconventional servo tracks having about the same physical space on tape.Thus, the areal density of servo information stored on magnetic tapesmay be increased in preferred embodiments, as will soon become apparent.

FIGS. 8A-8B depict a product 800 for storing data, in accordance withone embodiment. As an option, the present product 800 may be implementedin conjunction with features from any other embodiment listed herein,such as those described with reference to the other FIGS. Of course,however, such product 800 and others presented herein may be used invarious applications and/or in permutations which may or may not bespecifically described in the illustrative embodiments listed herein.Further, the product 800 presented herein may be used in any desiredenvironment.

Referring now to FIG. 8A, the product 800 includes a magnetic recordingtape 802 having opposite ends 804, 806. Moreover, a longitudinal axis808 of the magnetic recording tape 802 is defined between the ends 804,806 thereof. It should be noted that the magnetic recording tape 802 ofFIG. 8A is not drawn to scale, but rather is illustrated to show thefeatures of the present embodiment.

Furthermore, although the magnetic recording tape 802 is shown havingmultiple servo tracks 810, according to various other approaches, themagnetic recording tape 802 includes at least one servo track. Thus,depending on the magnetic recording tape 802 used, the tape may includeat least two, at least three, multiple, etc. servo tracks, e.g., forincreased accuracy, speed, etc. Referring back to FIG. 2A, the tape 208includes 9 servo tracks 210 in accordance with one illustrativeembodiment.

The magnetic recording tape 802 may be embodied with and/or in acartridge, such as cartridge 150 of FIG. 1A.

Referring now to the detailed view of FIG. 8B, the servo track 810includes a plurality of first magnetic bars 812 and a plurality ofsecond magnetic bars 814. Each of the first magnetic bars 812 preferablyhave a longitudinal axis, extending between opposite ends thereof, thatis oriented at an angle φ, between about 2 and about 88 degrees from thelongitudinal axis 808 of the magnetic recording tape 802, but could behigher or lower depending on the desired embodiment. Moreover, each ofthe second magnetic bars 814 have a longitudinal axis oriented at anangle θ that is ±45 degrees from the longitudinal axis 808 of themagnetic recording tape 802. In a preferred embodiment, the longitudinalaxes of the second magnetic bars 814 are each oriented substantially 90degrees from the longitudinal axis 808 of the magnetic recording tape802. Referring to the present description, “substantially 90 degrees” isintended to be within 1 degree of the stated angle (90 degrees), butcould be higher or lower depending on the desired embodiment.

A servo frame may be defined as an adjacent set of the first and secondmagnetic bars 812, 814. Thus, in one approach, the servo track may haverepeating sets of such frames. However, in preferred embodiments, theservo frames include additional bars. For example, with continuedreference to FIG. 8B, the servo track 810 has a plurality of thirdmagnetic bars 820 oriented to form chevron-like patterns with the firstmagnetic bars 812. The third magnetic bars 820 are also angled, e.g.,between about 2 and about 90 degrees from the longitudinal axis 808 ofthe magnetic recording tape 802. Note that the third magnetic bars 820may have an angular value similar to the angle of the first bars 812,but in reverse thereto at a negative angle. However, the angular valuesof the first and third magnetic bars may be different.

Moreover, as illustrated, the second magnetic bars 814 are positionedbetween sets of the first and third magnetic bars 812, 820 in a largerservo frame. The second magnetic bars 814 may be positioned away fromthe point of closest approach 822 of the first and third magnetic barsclosest thereto. Put another way, the second magnetic bars 814 are notcentered laterally in the servo track, but rather are positioned moretowards the wider part of the chevron-like pattern than the narrower“tip” region thereof.

As an option, the servo track may have a plurality of fourth magneticbars 824, the fourth magnetic bars 824 each having a longitudinal axisoriented ±45 degrees, and preferably substantially 90 degrees, from thelongitudinal axis of the magnetic recording tape. The fourth magneticbars 824 may be positioned closer to one side of the associated servotrack (top of the tape in FIG. 8B) than the second magnetic bars 814.

Note that FIG. 8B depicts a 5-5-5-5 pattern (4 sets of 5 bars) in eachservo frame 830. Alternative embodiments may have a 5-5-5-5-4-4-4-4 orany other pattern in a servo frame, such as an “N”-type pattern formedby some or all of the magnetic bars, an “M”-type pattern formed by someor all of the magnetic bars, a “V”-type pattern formed by some or all ofthe magnetic bars, etc. In this example, the shorter second and fourthbars 814, 824 are tucked in the otherwise empty and unused space betweenthe longer first and third bars 812, 820. The second and fourth bars814, 824 are shown orthogonal to the tape travel direction and thus maybe used to provide tape skew and tape velocity detection, which are anecessary component in timing based servoing. In this manner every groupof first and third magnetic bars 812, 820 can be used for positionrecovery.

With continued reference to FIG. 8B, the lengths of the second andfourth magnetic bars 814, 824 along the longitudinal axes thereof areless than the width of the servo track 810, where the width w₁ of theservo track 810 is defined in a direction perpendicular to thelongitudinal axis 808 of the magnetic recording tape 802 between sidesof the servo track. The sides of each servo track may be considered toextend along imaginary lines extending along ends of the first magneticbars. The width w₁ of the servo track 810 may be less than about 250microns, preferably less than 200 microns. The effective width of theservo reader is smaller, e.g., between 1 and 10 microns.

The lengths of the second and fourth magnetic bars 814, 824 are shorterthan the width w₁ of the associated servo track 810. For example, invarious approaches, the lengths of the second and/or fourth magneticbars 814, 824 are less than 85%, more preferably less than 80% of thewidth w₁ of the associated servo track. In some approaches, the lengthsof the second and/or fourth magnetic bars 814, 824 are between 33% and67% of the width w₁ of the associated servo track. The lengths of thesecond and fourth magnetic bars 814, 824 may be the same or different.In a preferred approach, the lengths of the second and/or fourthmagnetic bars 814, 824 are slightly longer than one-half the width w₁ ofthe associated servo track to enable decoding across the full width ofthe servo track 810.

In one particularly preferred embodiment, depicted in FIG. 8C as avariant of the embodiment of FIG. 8B, the lengths of at least some ofthe second and/or fourth magnetic bars are one half a width w₁ of theservo band, plus 0.25 to 3 microns. This range covers one half the trackwidth of present and future servo readers, and thus the servo readershould always be able to detect the second and/or fourth magnetic bars814, 824. Moreover, where both second and fourth magnetic bars 814, 824are present, the detection of both second and fourth magnetic bars 814,824 may be used as a reference indicative of the longitudinal centerline834 of the servo track 810. Such information may be useful, e.g., forcalibration during operation.

In another embodiment, depicted in FIG. 8D as a variant of theembodiment of FIG. 8B, the lengths of at least some of the second and/orfourth magnetic bars are one half a width of the servo band, minus 0.25to 3 microns. In this case, the lack of detection of second and fourthmagnetic bars 814, 824 may be used as a reference.

The timing between one of the first and one of the third magnetic bars812, 820 may be used in conjunction with linear tape velocityinformation to determine the lateral position of the head relative tothe tape.

The linear tape velocity information may be derived from selectedmagnetic bars in a single servo frame, e.g., by determining a timingbetween the first and last ones of the second magnetic bars 814 in oneservo frame, by determining a timing between the two of the fourthmagnetic bars 824 in one servo frame, the timing between one of thesecond and one of the fourth magnetic bars 814, 824; etc. The timing canthen be correlated to the distance the tape has traveled to compute thevelocity. Lookup tables may also be used. A benefit of deriving thetiming for determining the linear velocity using the second or fourthbars is that they are less susceptible to tape skew and other effects.Moreover, the timing may be determined within the frame, and used toquickly compute the lateral position using the chevron-derivedinformation, thereby enabling much faster lateral positioning. Inalternate embodiments, the linear tape velocity information may bederived using magnetic bars in sequential servo frames.

Spacing may be present between servo frames to assist the system indetecting the locations of the frames, e.g., by detecting the delaybetween servo frames.

In one approach, the tape skew may be detected by detecting an offset inthe signals of the servo readers above the parallel servo tracks as theydetect the second and/or fourth magnetic bars 814, 824. If no tape orhead skew is present, and the second and/or fourth magnetic bars 814,824 are aligned laterally on the tape, then no difference in the servosignals should be detected. If skew is present, the timing of the servosignal from one servo reader will be offset from the timing of the servosignal from the other servo reader. The magnitude and sign of thisoffset directly relate to the direction and magnitude of the skew. Thisis enabled because the second and/or fourth magnetic bars 814, 824 areoriented orthogonal to the longitudinal axis 808 of the magneticrecording tape 802.

As noted above, the sets of the magnetic bars may be grouped into servoframes 830. Preferably, a position of at least one of the first magneticbars in one of the frames is different than in other frames therebydefining encoded information in the servo track, as shown at 832. Inother words, one or more of the bars may be advanced or delayed by someamount that is detectable and usable to discern additional information.For example, such encoded information may include linear positioninformation, etc. Encoding schemes of a type known in the art may beused.

The magnetic tape 802 may be used by an apparatus such as that shown inFIG. 1.

FIG. 9 depicts an apparatus 900 to write the servo patterns onto themagnetic recording tape, in accordance with one embodiment. As anoption, the present apparatus 900 may be implemented in conjunction withfeatures from any other embodiment listed herein, such as thosedescribed with reference to the other FIGS. Of course, however, suchapparatus 900 and others presented herein may be used in variousapplications and/or in permutations which may or may not be specificallydescribed in the illustrative embodiments listed herein. Further, theapparatus 900 presented herein may be used in any desired environment.Thus FIG. 9 (and the other Figures) should be deemed to include any andall possible permutations.

The apparatus 900 may include one or more magnetic heads 902 each havingat least one servo writer 903 for writing the magnetic bars to themagnetic recording tape. Ideally, enough servo writers 903 are presentto write all servo tracks on the tape simultaneously. As shown, eachservo writer 902 has write gaps 904 oriented to write sets of themagnetic bars on the magnetic recording tape for creating a servopattern 810 as shown in FIG. 8B. However, in other approaches, thenumber and/or orientation of the write gaps 904 may be different,depending on the servo pattern to be written, as would be understood byone skilled in the art upon reading the present description.

The apparatus 900 may also include a drive mechanism for passing themagnetic recording tape over the magnetic head, e.g., as shown in FIG.1A; and a controller electrically coupled to the magnetic head, e.g., asalso shown in FIG. 1A. The controller may use known servo writingtechniques when controlling the magnetic head 902.

In operation, one or more servo tracks are written to a magnetic tape bythe apparatus. The write gaps 904 may each emit flux concurrently. Inother approaches, one or more of the write gaps may be separatelyaddressable from the other write gaps. Accordingly, suchseparately-addressable write gaps may be associated with a differentwrite coil and yoke than the other write gaps.

Furthermore, any of the embodiments described above may be implementedwith previous data and/or tape formats, generations, platforms, etc.Moreover, various embodiments described herein may provide additionalinformation for decoding tape skew within a single module rather thanusing servo readers on two modules, as conventionally required.

It will be clear that the various features of the foregoing systemsand/or methodologies may be combined in any way, creating a plurality ofcombinations from the descriptions presented above.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as “logic,” a “circuit,” “module,” or“system.” Furthermore, aspects of the present invention may take theform of a computer program product embodied in one or more computerreadable medium(s) having computer readable program code embodiedthereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a non-transitory computer readable storage medium. A computerreadable storage medium may be, for example, but not limited to, anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus, or device, or any suitable combinationof the foregoing. More specific examples (a non-exhaustive list) of thenon-transitory computer readable storage medium include the following: aportable computer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a portable compact disc read-only memory (e.g.,CD-ROM), a Blu-ray disc read-only memory (BD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a non-transitory computerreadable storage medium may be any tangible medium that is capable ofcontaining, or storing a program or application for use by or inconnection with an instruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof Acomputer readable signal medium may be any computer readable medium thatis not a non-transitory computer readable storage medium and that cancommunicate, propagate, or transport a program for use by or inconnection with an instruction execution system, apparatus, or device,such as an electrical connection having one or more wires, an opticalfibre, etc.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fibre cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer, for example through the Internet using an Internet ServiceProvider (ISP).

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart(s) and/orblock diagram block or blocks.

It will be further appreciated that embodiments of the present inventionmay be provided in the form of a service deployed on behalf of acustomer.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of an embodiment of the presentinvention should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and their equivalents.

What is claimed is:
 1. A product, comprising: a magnetic recording tapehaving opposite ends and at least one servo track, a longitudinal axisof the magnetic recording tape being defined between the ends; the atleast one servo track having a plurality of straight first magnetic barsand a plurality of straight second magnetic bars spaced from the firstmagnetic bars, wherein a width of each of the at least one servo trackis defined in a direction perpendicular to the longitudinal axis of themagnetic recording tape between sides of the servo track, the sides ofeach servo track extending along opposite ends of each of the firstmagnetic bars, wherein lengths of the second magnetic bars betweenoutermost ends thereof are less than the width of the associated servotrack.
 2. The product as recited in claim 1, wherein the at least oneservo track has a plurality of third magnetic bars oriented to formchevron-like patterns with the first magnetic bars, the second magneticbars being positioned between sets of the first and third magnetic barsin a servo frame.
 3. The product as recited in claim 1, wherein thefirst magnetic bars each have a longitudinal axis oriented between 2 and88 degrees from the longitudinal axis of the magnetic recording tape. 4.The product as recited in claim 1, wherein the at least one servo trackhas a plurality of fourth magnetic bars, wherein the fourth magneticbars are positioned closer to one side of the associated servo trackthan are the second magnetic bars.
 5. The product as recited in claim 1,wherein the lengths of the second magnetic bars are less than 80% of thewidth of the associated servo track, the second magnetic bars eachhaving a longitudinal axis oriented substantially 90 degrees from thelongitudinal axis of the magnetic recording tape.
 6. The product asrecited in claim 1, wherein sets of the magnetic bars are grouped intoservo frames, wherein a position of at least one of the first magneticbars in one of the frames is different than in other frames therebydefining encoded information in the servo track.
 7. The product asrecited in claim 1, wherein the lengths of at least some of the secondmagnetic bars are one half a width of the associated servo track plus0.25 to 3 microns.
 8. The product as recited in claim 1, wherein thelengths of at least some of the second magnetic bars are one half awidth of the associated servo track minus 0.25 to 3 microns.
 9. Anapparatus, comprising: a magnetic head; a drive mechanism for passingthe magnetic recording tape of claim 1 over the magnetic head; and acontroller electrically coupled to the magnetic head, the controllerbeing configured to decode the servo track(s) of the magnetic recordingtape.
 10. An apparatus, comprising: a magnetic head having at least oneservo writer for writing the magnetic bars to the magnetic recordingtape of claim 1; a drive mechanism for passing the magnetic recordingtape over the magnetic head; and a controller electrically coupled tothe magnetic head.
 11. A computer program product for writing servotracks on a magnetic recording tape, the computer program productcomprising a computer readable storage medium having programinstructions embodied therewith, wherein the computer readable storagemedium is not a transitory signal per se, the program instructionsexecutable by a controller to cause the controller to perform a methodcomprising: cause, by the controller, writing of at least one servotrack on a magnetic recording tape, the at least one servo track havinga plurality of first magnetic bars and a plurality of second magneticbars, wherein a width of each of the at least one servo track is definedbetween sides of the servo track in a direction perpendicular to alongitudinal axis of the magnetic recording tape, the sides of eachservo track extending along ends of the first magnetic bars, whereinlengths of the second magnetic bars between outermost ends thereof areless than the width of the associated servo track, the second magneticbars each having a longitudinal axis oriented substantially 90 degreesfrom the longitudinal axis of the magnetic recording tape.
 12. Thecomputer program product as recited in claim 11, wherein the at leastone servo track has a plurality of third magnetic bars oriented to formchevron-like patterns with the first magnetic bars, the second magneticbars being positioned between sets of the first and third magnetic barsin a servo frame.
 13. The computer program product as recited in claim11, wherein the first magnetic bars each have a longitudinal axisoriented between 2 and 88 degrees from the longitudinal axis of themagnetic recording tape.
 14. The computer program product as recited inclaim 11, wherein the at least one servo track has a plurality of fourthmagnetic bars, wherein the fourth magnetic bars are positioned closer toone side of the associated servo track than are the second magneticbars.
 15. The computer program product as recited in claim 11, whereinthe lengths of the second magnetic bars are less than 80% of the widthof the associated servo track, the second magnetic bars each having alongitudinal axis oriented substantially 90 degrees from thelongitudinal axis of the magnetic recording tape.
 16. The computerprogram product as recited in claim 11, wherein sets of the magneticbars are grouped into servo frames, wherein a position of at least oneof the first magnetic bars in one of the frames is different than inother frames thereby defining encoded information in the servo track.17. An apparatus, comprising: the computer program product as recited inclaim 11; a magnetic head; a drive mechanism for passing a magneticrecording tape over the magnetic head; and the controller electricallycoupled to the magnetic head.
 18. A controller-implemented method,comprising: causing, by the controller, reading of at least one servotrack of a magnetic recording tape, the at least one servo track havinga plurality of straight first magnetic bars and a plurality of straightsecond magnetic bars spaced from the first magnetic bars, wherein awidth of each of the at least one servo track is defined in a directionperpendicular to a longitudinal axis of the magnetic recording tapebetween sides of the servo track, the sides of each servo trackextending along opposing ends of each of the first magnetic bars,wherein lengths of the second magnetic bars between outermost endsthereof are less than the width of the associated servo track; andderiving, by the controller, at least one of velocity and skewinformation from reading the at least one servo track.
 19. The method asrecited in claim 18, wherein the second magnetic bars each have alongitudinal axis oriented substantially 90 degrees from thelongitudinal axis of the magnetic recording tape.
 20. An apparatus,comprising: a magnetic head; a drive mechanism for passing the magneticrecording tape over the magnetic head; and a controller electricallycoupled to the magnetic head, the controller being configured to performthe method of claim 18.